Fluid pressure motor



Dec. 8, 1953 G. ALFIERI FLUID PRESSURE MOTOR 2 Shee't's-Sheet l ILedFeb. 28, 1948 INVENT OR G/USEPPE ALF/ERI BY #uu/@56M 7:

AGENTS Dec. 8, 1953 G. ALFIERI FLUID PRESSURE MOTOR 2 Sheets-SheenaFiled Feb. 28, 1948 INVENTOR G/USEPPE Amm/ Patented Dec. 8, 1953 FLUIDPRESSURE MOTOR Giuseppe Alfieri, Milan, Italy Application February 28,1948, Serial No. 12,125

In Italy March 18,1941 f section 1, Public Law 690,*August s, 194ePatent expires March 18, 1961 6 Claims.

This invention relates to reciprocating pressure fluid operated motorsof the type used in actuating windshield wipers or other similar vehicleaccessories.

A general object of this invention is to provide a pressure fluidoperated motor of the type described Which is simple and compact inconstruction and trouble-free in operation.

According to features of this invention, the above general object isrealized by providing a pressure fluid operated motor including a casingformed with two opposed cylinders of different diameter, each having apiston working therein, and a hollow connecting rod extending betweenthe pistons so that the latter move as a unit. A pressure fluid inlet isformed in the cylinder of smaller diameter so that the piston therein iscontinuously exposed to the pressure fluid, and a pressure fluidpassageway extends through the connecting rod for communicating thelarger diameter cylinder with the smaller diameter cylinder. A pressurefluid exhaust is provided in the piston working in the' larger diametercylinder, and communicates with the section of the casing between thecylinders, whi-ch section is open to the atmosphere. A valve stemextends slidably through the connecting rod andthe pistons, and the stemcarries a first valve at the end extending into the smaller diametercylinder for closing the pressure fluid passageway and a second valve atthe end extending into the larger diameter cylinder for closing thepressure fluid exhaust therefrom. The stem is of such length that thevalves at the opposite ends thereof are alternately seated, and furtherthe stem is provided with resilient bumpers at its opposite endsengageable with the respective cylinder heads, when the pistons reachthe ends of their stroke in each direction, to thereby shift the valvestem for actuating the valves. Therefore, the pressure fluid enteringthe smaller -cylinder will initially seat the first valve, whichY causesunseating of the second valve, so that the pressure fluid passageway tothe larger cylinder is closed and the exhaust from the latter is open,and the piston unit is driven in the direction towards the largercylinder by the pressure fluid in the smaller cylinder acting againstthe piston in the latter. When the piston unit reaches the limit of itsstroke towards the larger cylinder, the bumper on the end of the valvestem extending through the larger piston engages the head of the largercylinder and shifts the stem for openingthe pressure fluid passagewayand closing the pressure fluid exhaust. The larger Qylllder lis @therebyfilled with pressure fluid, and since the area of the larger piston isgreater than that of the smaller piston, a resultant force will beapplied to the piston unit for moving the latter back to its initialposition. At the limit of this reverse movement, the valve stem is againdisplaced to close the pressure fluid passageway and open the exhaustpassageway. Thus the piston unit continuously reciprocates in thecasing.

Further, according to this invention, the connecting rod is formed witha gear rack thereon, which meshes with a gear segment disposed in thenon-pressurized section of the casing between y the cylinders and fixedon the shaft driving a a pressure fluid operated motor having thecharacteristics and features noted above, wherein the driven shaft isformed with a suitable passageway for communicating the section of thecasing n between the cylindersfwith the atmosphere, so

that the exhaust of pressure fluid from the larger cylinder will be at apoint remote from the casing; and in particular, when the shaft operatesa windshield wiper, so that the exhaust of such pressure fluid will beat the end ofthe shaft outsideof the vehicle. 4 1

A further Objectis ,to provide a pressure fluid operated vmotor havinga'driven shaft formed with apressure fluid exhausting passageway,wherein such pressure fluid exhaustingpassageway is so formed as toeffect ejection of condensate forming within the casing. r

Still another object is to provide a, pressure fluid operated motor ofthe kind described wherein the valve for closing the exhaust passagewayfrom the larger cylinder, when seated, effectively seals such Vexhaustpassageway from communicationwith the pressure fluid passagewayextending through the hollow connecting rod, so that-no sealing meansare required around the valvestem, thereby simplifying the constructionand reducing the frictional forces to be overcome in moving the valvestein. 1 Y. e.

' A V5.1111 further object ,is to provide a pressure' fluid `operatedmotor of the class described in.

ending Lstepping means for rendering che motorA These and other objects,features and advantages of the invention will appear in the followingdetailed description of several illustrative embodiments thereof, whichdescription is to vbe l read in conjunction with the accompanyingldrawings forming a part thereof, and wherein:

Fig. l is a longitudinal, sectional view-along the axes of the cylindersof a pressure fluidrpperated motor constructed accordingtofanfembodimentof this invention;

Fig. 2 is a longitudinal sectional View along the axes of thecylindersof a pressure fluid operated motor constructed according toyanotherembodiment-.fof this-invention. `@nel in'cliidill a driven shaftconstructed to exhaust Athe-pressure fluid ata point remote from -themotor casing;

Fig. 3 is a transverse, `sectional view taken along theline 3-,3 of Fig.2;

Fig. .4 is a longitudinal, sectional view along the axes of thecylinders'ofa pressure fluid operated-motorconstructedaccording to stillanother modicationof -the invention, Lwherein the valve closing theexhaust 'port from the larger cylinder also isolates rthe exhaustpassageway relative .to the pressure fluid passageway;

Fig. 5 is a longitudinal, sectional view of a pressurefluid operatedmotorsimilar to the form illustrated in Fig. Il, and including a ;stopping mechanism carried bythehead of the smaller cylinder;

Fig.- 5Ais a view partly `in-section taken along the hline 5A-5A ofFigure 5; and

1 Fig. 6 is a longitudinal,"sectional'view of a pressure fluid operatedmotor combiningthe valve formation of the'form illustrated Fig. 4l andthe stopping mechanism of themodiiication illustrated in Fig. 5.

Referring initially toiliig.` 1' of the drawings, the pressurehuid-operated motor there illustrated includes a two-sectionfcasingIformed with opposed cylinders of different vdiametersy in therespective sections thereof. The cylinders are axially aligned and opentowards each other, with the cylinder of smallerdiameter, hereinafterreferred to as vthe smaller cylinder, being indicated by referencenumeral 2, and withthe cylinder-of larger? diameter, .hereinafterreferred" to' as the "larger cylinder, being indicated by -the'reference numeral`3. "CylindersZ and'A 31 arefspacedapart at theirconfronting open ends'and open-into an enlarged section 29 of 'thecasing I corresponding to'a crankcase. Smaller cylinder 2 is providedwith a Apressure fluid inletl 4, in the head thereof, for connection toasource'ofjpressure fluid (not shown) Pistons 5 andi 6, uof suitablediameter, work in cylinders and 3, respectively, and are rigidlyconnected together' bya hollow connecting rod 1 so that pistons 5 and k6reciprocate in unison, with pistons 5; and' 6, and connecting rod 1hereinafter being referred to as1apiston unit. The pistons 5-and` 6 areprovided with annular packing's 8- and 9, respectively, of;conventionalform for sealing the pistons relative to their respecti've cylinders. -Adislf. I0 `is .fixed to the vhead Qf Cylesel ,land isormcd'withamarginal rib or rifdge dimensioned to.fbe receivedinthean-g nular recessof 'packing 9'to thereby th@ dead space in cylinder 3 when the pistonunit has reached the limit of its stroke towards the larger cylinder.

Connecting rod 'I' is formed with a series of longitudinally spacedteeth on the exterior thereof constituting a gear rack I I which mesheswith a spur gear segment I2 iixed to shaft I3. `Shaft I3 is journalledin the casing I, for reciprocation about an axis disposed at rightangles to the axes Aof the cylinders and offset therefrom, and extendsout of thecasing for connection to a windshield wiper (not shown) orother vehicle accessary operated by an oscillating driving shaft. It isapparenttha-t gear-rack I I and gear segment I2 are effective totransmit reciprocatory motion of the :fpistonunit to they driving shafti3, for oscillating :the latter.

I n order to provide for the reciprocation of the piston unit, thepressure fluid operated motor of Fig. 1 further includes a system forselectively and automatically controlling the distribution of pressurefluid in the respective cylinders. This system includes a bore I5extending axially through connecting rod 'I and opening at one end intocounter-bored chamber 20, of increased diameter, formed in the outerlsurface of piston 5. The bore I5 is enlarged adjacent its other end andopens into a counter-bore ZI of increased diameter formed in the face ofpiston 6. A valve stem I4, of substantially smaller diameter than thatof bore I5, extends loosely'through the latter, withan annularpassageway being defined between the stem and the surface of the bore. Aferrule 26 is threaded into the enlarged portion of bore I5 andl isformed with a central opening through .which stem I4 Aloosely extendsleaving an annular space 21 therebetween. Counterbore 20 is formed withan annular ridge on its bottom surface around the opening to bore I5 toprovide a valve'seat I8, and ferrule 26 is formed with a similar annularridge on its outer face, extending into counter-bore 2I, to provide avalve seat I9. Valve members I6 and I'I are fixed on the opposite endsof stem I4 for seating against valve seats I8 and IB, respectively. Asseen in Fig. l, valve members I6 and II have diameters that are lessthan the diameters of counter-bores 20,and 2I so that the valve membersmay work in the respective counter-bores while providing an annularspace for the passage of pressure fluid. Further, valve members I6 andI1 are so positioned on the stem that the valve members arealternatively seated. That is, when stem I4 is positioned to seat valveI6 on seat I8, valve I'I is removedV from seat I9, and when stem I4 `ispositioned to seat valve I'I on seat I9, valve I6 is unseated..

Packing 241s disposed in the enlarged portion of'bore l5, Withstem I@extending slidably therethrough, and is urged against the shoulder,formed between-the enlarged porti-on of the bore and the smaller portionthereof, by spring 25 abuttingagainst the innerV surface of ferrule 25'.Packing 24 then isolates thepassageway formed between bore I5 and steinIll, and opening into counter-bore 20, from the'chamber donnedbetweenthe enlarged portion ofthe bore and stem [Land opening throughannular space 21 into counter-bore 2I.

A by-pass 3l is formed in connecting rod 'l and piston .6, opening atits opposite ends into cylinder' through the face of piston G andA intob ore `Iflaliead of packing 2t. y By-pass 3i and theportion o f bore 15opening into counter`oorei2,pro"- vide communication between cylinders 2and 43 `uid passageway to cylinder 3.

ing the shaft clockwise. reaches the limit of its movement towardcylinder -3, spring 23 engages the head ofthe latter, and

lclockwise. .limit of its movement towards cylinder' 2, spring .22engages the head of the latter to shift stem i4 A port 28 is formed`radially in coninto the enlarged portion 'of the bore between ferrule26 and packing 24. Annular passageway 2l, the enlarged portion of thebore, and portA 28 provide communication between cylinders 2 and 3, whenvalve I'I is unseated, and are hereinafter collectively referred to asthe pressure fluid exhaust passageway. 'form of 'a slot, opens thecasing section between A leak passage 30, in the Vthe cylinders to theatmosphere.

i Finally, coil springs 22 and23 are fixed on the :opposite ends of stemI4,. outwardly of pistons K and 5, respectively, for engagement with thecylinder heads at the oppositeextremes of the vstroke of the piston unitto effectshifting of valve stem I4.

Operation of the pressure fluid operated motor -illustrated in Fig. l isas follows:

l Pressure iiuid, such as compressed air, is 1ntroduced into cylinder 2through-inlet 4. -pressure fluid in cylinder 2 acts against valve I5 Theto seat the latter and thereby close the pressure With valve I6 seated,valve I1 is unseated to open the pressure fluid exhaust passageway fromcylinder 3. The

pressure fluid in cylinder 2 also acts against piston 5 to move thelatter and the other elements of 'the piston unit toward cylinder 3, ortoward the `right as viewed in Fig. 1.

Such movement `of the piston unit is transmitted by meshing gear rack IIand gear segment I2 to shaft I3 thereby rock- When the piston. unitvalve stem I4 is thereby moved relative to the piston unit to seat valveI1 and unseatvalve i6.

l-With the valves so disposed, the exhaust passageway from cylinder 3 isclosed, and the pressure fluid passageway from cylinder 2 to cylinder 3is open to lead pressure fluid into the latter. Since the area of piston6 is greater than that of piston. f

5,r the pressure fluid acting in opposite directions against both willprovide a resultant force which acts on the piston unit tomove thelatter back towards cylinder 2, or toward the left as the motor isviewed in Fig. l. This return movement of the piston unit is transmittedby gear rackv H and gear segment I2 to rock shaft I3 countcr- When thepiston unit approaches the relative to the piston unit for seating valvei5 closing the pressure fluid passageway, and for -unseating valve I'Iopening the pressure fluid exhaust passageway from cylinder 3. Thepressure fluid then only acts against piston 5 to .move the piston unitback towards cylinder 3, and as the piston unit is so moved, thepressure fluid in cylinder 3 is exhausted therefrom through the exhaustpassageway into the casing section between the cylinders and thence tothe atmosphere through slot 3U. Thus the piston Vunit is automaticallyreciprocated in the casing and shaft I3 is correspondingly oscillated. 1

As previously indicated, disklIil-fits into the annular recess ofpacking 9, when the piston unit 4reaches the limit of movement towardsthe head .ofcylinder 3,A to thereby decrease the dead space .inthelattenA similar disk is not required in .cylinder .2, since pressure fluid.Vis continuously` present in the latter.

.mosphera The Ygroove 38 is preferably'screw shaped, as

the friction of the sideedges thereof .sure fluid operated motorconstructed according .to this invention is'there illustrated, which` issimilar in its major components to the motor shown in Fig. landdescribed above. The motor shown in FigsjZ and 3 includes a casing Iformed with opposed cylinders 2 and 3 of different diam- .eters openingintovtheintermediate section 29. Theiintermediate section of this casingis distinguished from Ythat of the motor first described in that lt isnot provided with an opening to the atmosphere. `As in the motor shownin Fig. l,

.a piston unit worksinthe casing, and includes a piston 5 in cylinder 2,a'piston 6 in cylinder 3 and a hollow connecting rod 'I. A valveassembly, similar to that already described, is carried by the pistonunit and alternately opens and closes the pressure fluid passagewaybetween cylinder 2 and cylinder 3 and thepressure fluid exhaustpassageway from cylinder Sto casing section 29. The several passageways,and structure by which they are defined, are similar to those previouslycletailed, a gear rack I I is formed on connectingrod 'I and meshes withgear segment i2 fixed on shaft I3 which extends into a lateral extension.29 of the intermediate casing section 29.

The motor of Figs. 2 and 3 is distinguished from that previouslydescribed in the following respects. A valve 32 is interposed betweenthe pressure fluid inletA 4 and the port opening into cylinder 2. Valve32 is of conventional construction and serves to control the rate of.flow of pressure fluid into cylinder 2 and hence the speed of themovement of the piston unit.

A shaft 31, extending parallel to shaft I3, is fixed in the intermediatecasing section 29 and extends out of the casing at one end to provide `amounting member. rod I removed from rack `I I and rotatably carries agrooved roller 36 in engagement with the connecting rod to stabilize thepiston unit during itsr reciprocation. f

An open ended tubular sleeve 33 (Fig. 3) extends iixedly from portion 29of the casing, with the shaft I3 rotatable therein, and projects out of.the compartment within-which the casing I is .mounted Bearings 34 and35 are carried at the opposite ends of tubular sleeve 33 forsupporting,r shaft I3 in the latter. yA bearing 42 is carried by casingsection 29 and` supports the inner end of shaft I3, which inner endcarries an `operating :hadle 40. Packing 4I lseals f casing section 29 varound the inner end of shaft I3. The arm 43 of lfrom casing sections 29and 29 to the atmosphere at a point outside of the compartment housing.the motor, a groove 38 is formed in thesurface ,of shaft I3 and extendsfrom inwardly of bearing 35, where it opens intoLgap39 between the hubof gear segment I2 and the bearing, to communi cate wlth'the casingsections 29 and 29'; to the outer end I3 of the shaft Where it opens toatshown inxFig. 3, to provide better distribution of upon the surfacesof bearings 34 and 35. The screw shape vof groove 38 in oscillated shaftI3 has Vthe further Shaft 31 is at the side oflVneutra,.uta-gefofpromoting; hegeiectionofiiceiormaitionsgthatgmaynabeformedrfromf the-condensate :carried-by thef'pressure luid .('suclrl ascompressed air) when it is beingxhaustedf Toiobtain'the greatestadvantage :of` the specific; construction Yhere-set forth, the casing`should .bei mounted with zzthesection 29' lowermost,:so that condensatewill :drain into this section, and .the .groove-)S should preferably bepositioned on. the Vshaft so that-.the inner endofthe groove willbelowermostwhen the .blade arm v4? isat` one'fofthe'extremes of'its:movement Thus condensate? "willnot frise :in section 29': above :thelower edge "of shaft I'3,:and .cannot accumulate 'sufficiently to :entercylinders 2. and '3 andnterfere withzoperation of theznotor. Ithas beenfound that'thepitch of screw shaped groove 38 is preferably twice-thelength -thesec- 'tion of shaft I3 in which it is formed for optimumejection of condensate.

While .theillustrated embodiment shows groove 38 formedin the surface of"shaft .I3,`.which arrangement'is preferable, exhaust of thepressurefluid at a point external of the vehicle comp'art- 1 ment in which themotoris'mountedfcould ibe-ob- 'tained iby forming Vthe groovein bearings34v and l -35, or by providing shaft I3 with an axial internalpassageway, these latter variations not being illustrated.

Referring .now to Fig. 4, a pressure `fluid operated motor is vthere`illustrated lin which Vthe .valve assembly andthe pressure --fiuiclpassageway and pressure fluid exhaust passageway-are :constructed andvarranged to avoid-'the'necessityf Vprovidingv packing, similar-topacking'24 inFig. 1,' to isolate the pressure Yiluid passageway-'from the'exhaust. l

The motor shown in Fig. 4"in`cludes a casing I having opposedcylindersZand-3 offdiierent diameters opening into the intermediate -se'c'tion 29,

a pressure fluid inlet 4 opening linto cylinder 2,

pistons 5 ands working in cylinders 2 andf, respectively, a connectingrod 'I joining the pistons, a gear rack I I formed on the AIconnectingrod, and a gear` segment I2 meshing lwith rack I I. andxed to the drivenshaft I3.V

The pressure fluid passageway in thisfmodie'd form includes a bore I5extending axially through 'the connecting Arod 'I and opening at one'end .through `the face of pistoni.' The bore lI 5 is formed withaportion of reduced diameter, or constric- .tion 43, at its otherend,an`d a valve sten-114 extends through bore I5 and is slidable'withinconstriction. The pressure 'fluidpassageway-is rcompleted by a bore44,-' inclined relative to the axis of the `.connecting rod,'Which'op'ens atfone end -into bore I5 ahead of constriction -43 andfatthe other end through the face' ofpistont at a point spaced radiallyfrom the' center thereof.

` Piston 5 is formed with an annularridge on theouter face thereofconcentric with the open end of bore I5, to provide a'valve seat; andpiston 6 is provided -withtwo radially*v spaced" annular ridges yorribsV48 and 41,' on the outer vface thereof, concentric with .the axis ofstem I4. The outermost rib 46 is spaced vinwardly from the lend vofpassageway 44 opening-into cylinderiB. "An exhaustpassageway is formedin ipiston vSeand opens at oneend intov the casing section29g which isventedl to the atmosphere in .the manner of .the motors shown in eitherFig. l or Fig. 2, andiatlthe otheriend into the channel formedin'..the/.face of piston' t. betweenannular, ribs ylIii-iandl.; :The:valveiassemblyincludesiralre members I5 Yand I1; oft disk-likeconnguration,1arranged .on theoppositef ends of: .stem A1415eralternatefseatis Ling",irespectivelygyagainstathe ann'ulafsrih' omniston15,. .to .close ;theA pressure fluidzpassagewaybe- Atween cylinder12.;.and l.cylinderzs and/.ragainst ribs V fand Y-4'11 pn piston .6.vvlfthen valve 'member I 1 seatsz-against ribs A5 vand-'4.1, thechanneled@- fined between these 'ribs ris-.closed thus isolating exhaustpassageway 45 fromrcylinderizas'well:as from the opening. inipiston 6-throughvwhich stem I4 extends. Therefore; by reasonoftheespecicconstruction of .its fseat, avalve I'l, when-seated serves the-dual-functionfof closing the exhaust from cylinder 3,1and alsoof isolatingthe fexhaust from the pressure .fluidwpassageway .toivthereby eliminatethe necessity of Lpacking 24 ,in the previously VdescribedmodificationIwhich serves lthis latter function. .As in the :previous .forms of :theinvention, springs-22l andaf :extend fromithe opposite ends off'stem'14, and engage ywithrthe .adjacent cylinder-@heads -at- .the :limits`otvthe stroke of the piston unit to effect the shifting Vtof the valveassembly. The operation of this-modification is similarxto that;previously Idescribed in connection-withzthemotor illustrated 1.

Referring now to Figu;y a pressure fluidiop- 'erated motor is l.thereshown whieh'issimilarfin construction to -thevdevice illustrated tin.Fig., 5l, withthe exceptionfof `the-head of-cylinder 2,"that is, thecylinder'of fsmaller diameter. v l

In this modified form, a Ystopping-.Yassernblyd incorporated `in -thehead y of the smaller lcylin der so that the piston unit may beselectively iretained at the end of `its :stroke towardicylinder 2. Thestopping yof zthel piston unit tin -this-position is achievedbyselectively removingzthe portion of the headVA against which spring 221Ais engageable from the Ipath sof ltravel'fof 'the spring so that thevalve stem-I4 is not-shiftedatzthe end of the stroke to 'close' thepressure fluid passageway and vopen -the lexhaust passageway vtromcylinder 3.

In the preferred embodiment,- the stoppingassembly includes Wingsor-gillsf52 `projeating-:axially from the end 5I ofA cylinder-ladiacentthe side wall of the latter towards the rpiston 5f forengagements/ith the latter. Wings 52"serve to limit the movement `of thepiston. :unit: towards cylinder 2. The wings 52 are disposed so fasltopermit spring 22 and thevalve TIG `to extendioutwardly therebetween. End551 vof Vcylinder*2-:-i's formed with'al cylindricalchamberafSLioper'u'ng into the cylinder between the Wings=52 andslidably receiving af'disc 53. A stem 55 is formed integral with disc 53and 'extends outwardly through the end wall or" chamber.' 54, andpacking 56 extends around 'stem'5`5 to prevent-leakage of the pressurefluid through the end wall of the chamber. `A cap 53 is threadedyasat51, onto the outer surf-aceof the structurefdening chamber 54, andengages the outer end ofy stem to control the position of stem55=and1ffthere by thatof disck 53. .Thelthreadsl .aref heldiinfrictional engagement, to prevent inadvertent turning of cap 58; by acoilfspring. 59, Adisposed-in an annular channel 602 formed-in the cap,land bearing against the cap' andthe end 5I1`o'f 'the cylinder. Rotation.of.' cap 58. is limitedy Aby engagement of a screw V612 carried bythecap-vvifth a stop or lug 6I formed on the zouten-endofthe structuredefiningschamb'er :54 .andv-proccting into 'the :pathI ofY travel `ofthe screw.

The pressure. iiuidgin:` cylinder 2continuously acts against disc 53; tomaintairrstemeif.ini-engagement with cap 58, andthe .severalsparts de'-`scribed abover :are Ypropcntional:andi arranged-iso that, when the capis screwedcontoithe cylinder 2, to thelimit of its movement inthatdirection, disc 53 projects axially into the path of travel ofspring 22 to shift valve stem I 4 before the wings 52 engage piston 5,to thereby insure the normal operation of the motor as previouslydescribed. However, when the cap 58 is rotated to increase the distancebetween the inner surface thereof and the wings 52, the pressure fluid,acting against disc 53, moves the latter axially outward out of the pathof travel of spring 22 when piston abuts against wings 52. Thus, whenthe disc 53 is removed from the path of travel of spring 2'2, theresultant force derived from the action of the pressure fluid againstboth pistons 5 and 6 will retain the piston unit against wings 52, andthe valve assembly will not be shifted at the end of the stroke from theposition in which the pressure fluid passageway between cylinders 2 and3 is open and the exhaust passageway from cylinder 3 is closed.

From the above, it will be seen that thepiston unit is positivelyretained in the stopped, or inoperative position, by the pressure iiuid,and therefore, the device operated by shaft I3 will be held in theinoperative position even when subjected to shocks or jarring.

To start the pressure fluid operated motor of Fig. 5, it is onlynecessary to screw cap 58 onto the cylinder head to thereby urge disc 53against spring 22 and shift stem III for closing the pressure iiuidpassageway between the cylinders and for opening the exhaust passagewayfrom cylinder 3. Then the device assumes the normal operation heretoforedescribed.

The stopping assembly has been illustrated in connection with a motorconstructed in accordance with the modification of Fig. 1, however, asillustrated in Fig. 6, the stopping assembly may be suitablyincorporated in other motors of similar construction, as, for example,the illustrated pressure fluid operated motor having the passageways andvalve assembly of Fig. 4, and the remote pressure fluid exhaust featureof Figs. 2 and 3.

Having thus described several preferred em" bodiments of this invention,it is to be understood that various changes and modifications, obviousto those skilled in the art, may be effected without departing from thescope of the invention which is intended to be defined in the appendedclaims.

I claim:

1. A reciprocating pressure fluid operated motor comprising a casingdefining a pair of opposed cylinders of dierent diameters; a piston unitreciprocatable in said casing including a piston working in each of saidcylinders and a connecting rod extending between said pistons; pressurefluid inlet means opening into the smaller of said cylinders so that thepressure fluid continuously acts against the piston in said smallercylinder; a pressure iiuid passageway for communicating said smallercylinder with the larger of said cylinders and extending through saidconnecting rod and opening at one end through the piston in said smallercylinder; a pressure iiuid exhaust passageway for communicating saidlarger cylinder with the atmosphere and opening at one end into saidlarger cylinder through the piston in the latter; a valve seat on eachof said pistons at the respective open ends of said passageways coaxialwith each other and with the longitudinal axes of said pistons; valvemeans for closing said passageways carried by said piston unit andactuated lby engagement with the heads of said cylinders when saidpiston unit approaches the limits of its travel l 10 Y in oppositedirection including 'a rst' valve'fo seating against the seat on thepiston in said smaller cylinder and a second valve for seating againstthe seat on the piston in said larger piston; and a Valve stem extendingthrough a bore in said connecting rod and carrying said first and secondvalves at the opposite ends thereof. y

2. A reciprocating pressure fluid operated motor according to claim 1;wherein said bore opens at one end into said valve seat on the pistonAin the smaller cylinder to constitute a portion of said pressure fluidpassageway; and including sealing means in said bore to prevent flow ofpressure liquid into saidlarger cylinder around said second valve, aby-pass passage formed in said rod and said piston in the largercylinder openingat its opposite ends into said larger cylinder and intosaid bore at a point ahead of said sealing means to complete saidpressure fluid passageway, and an exhaust port formed in said rod andopening into the portion of said bore after said sealing means, saidlast mentioned portion of said bore opening into said valve seat on thepiston in the larger cylinder and with said exhaust port constitutingsaid pressure fluid exhaust passageway. l f

3. A reciprocating pressure fluid operated motor according to claim 1including a fixed abutment in said smaller cylinder limiting themovement of said piston unit toward said smaller cylinder, and axiallymovable means carried by the head of said smaller cylinder engageablewith said stem in one position to shift the position of the latterbefore said piston unit engages said xed abutment and removed from thepath of travel of said stem in an axially displaced position to rendersaid motor inoperative with said piston unit against said fixedabutment.

4. A reciprocating pressure iiuid operated motor according to claim 3;wherein said valves are positioned to open said pressure fluidpassageway and to close said pressure fluid exhaust passage- Way duringmovement of said piston unit toward said smaller cylinder, whereby, whensaid axially movable means is in said axially displaced position, saidvalves retain their respective positions so that the pressurefiuidcontinuously urges said piston unit against said fixed abutment.

5. A reciprocating pressure fluid operated motor according to claim 4;wherein said axially movable means includes an axially slidable stemextending through the head of said smaller cylinder, a disc on the innerend of said stem for engagement with the adjacent end of said valvesteml a cap threaded on said head and limiting outward movement of saidaxially slidable stem, means limiting the rotation of said cap, andspring means acting on said cap for frictionally retaining the latter inselected position.

6. A reciprocating pressure fluid operated motor comprising a casingdefining a pair of opposed cylinders of different diameters; a pistonunit reciprocable in said casing including a piston Working in each ofsaid cylinders and a connecting rod fixed between said pistons; pressurefluid inlet means opening into the smaller of said cylinders, a boreextending axially through said rod and open at its opposite ends throughthe outer faces of said pistons, a first valve seat formed at the end ofsaid bore opening through the smaller piston, a portion of reduceddiameter formed in the end of said bore adjacent the larger piston, avalve stem slidable in said bore and extending out of the opposite endsthereof, a by-pass formed in said rod and larger piston opening at oneend 11 iwtlsald bore ahea'df offsaildiprtn foreduced lametrffand iatth'e'otherf-'endl through she fouter fafe (of'fsai'd laiger piston/atfaip'oint spaced radially. frmilthe-adicent .open' Fendt of isaidlbore; a; pair olr'diall-y spaced :apa-rt ribs formed-fon the 'outerfa'cefof saidlarlger piston fconcer'ltricwith said bore to provde'a.second valve seat. the ouerfone ofsaffri'bs -bein'g` spaced inwardly:from said-futher end"of'=said vlay-passi 'a pressure uid exhaust!pa.ssgew-ay extending.- through said-'large'rpiston and bpenfllgthroughthe 'outer facerdi thelatter betwmfsaid annular ribsl-atrstvalveonfoneend f saidst'em for seating against said rst seat and i'secondvalve'onthe'bther end oil said stem'for seating -zafgirxst said parnf ribs totherebyisolate said' exhaustv 'passageway from- A`said: bore, saidvtlves-bengdisposedfon said stemK -foi` alternate seating; :and :means-on the opposite ends -ofsa-i'd stemngageable: with ther-heads of saidcylinders toyslirlftsad stemvaxial-1y at the end of lthelpiston urtstravel in either directio'n.

GiUsEPPE im" "I:

Number

